Belphanior -
We don't use critical hits on spells. A few points:
First, and I realize that this is a personal point of view, not statement of fact - I think that 3E spellcasting is overpowered at middle levels and above. In my experience, by 12th level, while fighters are still necessary for a party, they are just shock absorbers to give the party mage time to do the real damage. In my mind, anything that makes melee combat more scary/effective is key.
Secondly, and this relates to how the point above affects my campaign, remember that spells in my campaign are limited. Because no more than half of a character's levels can be taken in a spellcasting class, characters won't get raise dead, heal, teleport, etc., until 18th+ level. I expect the party will be dead long before then

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Q: what about more difficult saves at higher levels? (paraphrased)
candidus_cogitens -
Because of the lower-powered nature of my campaign, and the focus on humanoid enemies, we're not going to be seeing a lot of dragons, etc. We'll just be going up against more, or more skilled, people like us. This just isn't the kind of campaign where we'll be taking 100 points of damage from a single blow.
I do think you've got a good point regarding standard campaigns. Here's one idea - rather than rolling a fort save bonus, you could compare the damage dealt to the base number of HP to determine severity of effect. For instance, a guy with 35 HP currently and 100 HP max who takes a 25 point blow would look on the 25% line; probably a medium-type effect. Just a thought; you might want to play around with this. You lose the save but gain consistency and level scalability.
Wow that system is so cool!!! Good job. I think that I'm going to use it.
Elvinis75 -
Glad you like it. I'd consider the stuff other people are saying, though, before just dropping it into a standard campaign. It might be a little too deadly for higher-magic worlds where people are doing crits more often and for more damage; you could use the alternative system above or just scale up how badly you have to miss the save to get these effects (in other words, you could do stuff like change the 11-15 line to the 20 - 30 line).
Thanks.